I believe the behavior is that it uses an electronic first-curtain shutter and mechanical second curtain (to close the shutter while it performs the read-out)
But I’m wondering if you’re asking two un-related questions.
Time-lapse modes typically mean you’re going to be capturing frames over a very long period. Live-view goes through a lot more battery power and extended use of live-view not only goes through battery power, but also heats the sensor (which will result in more thermal noise.)
If you prefer to use live-view to compose and focus for a time-lapse... you may want to turn off live-view when you start your capture sequence just to make sure you don’t run out of battery.
The 5D IV does have a “silent shutter” mode (it’s not really silent) ... which slows the mirror speed to quiet down the mirror slap (that’s most of the noise you hear when you take a shot... the shutter curtains themselves aren’t very noisey). You WILL still hear the shutter sound (it’s not silent) ... but it’s a little more of a slushing sound rather than a snapping sound.
Tim Campbell
5D III, 5D IV, 60Da
